This invention relates to a boat dock and boat lift, and more particularly to such a combination dock and lift which has a lift movable between a lowered position below the surface of the water in which a boat may be floated into position above the lift, and a raised position in which a boat supported on the lift is lifted clear of the water.
More generally, it is a relatively common practice to remove smaller pleasure boats, such as outboard runabouts and the like, from the water when not in use so as to prevent the growth of marine life (e.g., barnacles and plant life) on the submerged portion of the boat hull. It is well known that such marine life must be periodically removed from the boat hull, or the performance of the boat will deteriorate markedly due to higher drag as the boat is propelled through the water. In order to prevent the growth of marine life on the hull of relatively small boats, the boats are oftentimes hoisted from the water when not in use. The hoisting of the boat from the water also enables the ready cleaning of the boat.
A variety of boat lifts or hoists are known. Heretofore, one such hoist involved a pair of davits which were secured to a dock or sea wall, and which extended out over the water. Block and tackle arrangements were carried by the end of the davits which, in turn, were connected to the bow and stern of the boat. By taking in or letting out the ropes or cables on the block and tackle arrangements, the bow and stern of the boat may be raised or lowered. However, such block and tackle davit lifting devices would raise or lower the bow or stern of the boat independently of one another. Thus, either two persons were required to raise or lower the boat, or one end of the boat could only be raised a relatively short distance (e.g., a foot or so), then that block and tackle arrangement secured while the other end was loosened and raised or lowered an appropriate amount so as to maintain the boat in a generally horizontal position as it was raised or lowered from the water.
Other boat lifting devices were known in which the above-described block and tackle arrangements were replaced by a horizontal pipe journaled on the ends of the davits, with a pair of cables attached to the pipe at each end thereof proximate the davits, and with the cables being connected to the bow ano stern of the boat. Upon rotation of the journaled pipe, as by means of a large hand wheel affixed to one end thereof, the pipe served as a winch which would uniformly raise or lower both ends of the boat substantially simultaneously. Of course, in place of the hand wheel, a motorized drive may be employed.
However, the use of such lifting cables required that the boat to be lifted have sufficient structural strength at both ends of the boat, together with hardware of sufficient strength, such that the weight of the boat can be supported by the bow and stern hardware and structure.
Other boat dock and lift apparatus were known in which an upright frame was provided adjacent the water, with the frame being secured to a dock or sea wall. The frame included two spaced upright beam members and a lift movably supported on the upright beams and having a pair of generally horizontal arms which extended outwardly from the beams forming a cradle engageable with the hull of a boat. A cradle arrangement was oftentimes provided on the horizontal lift arm so as to conform to the shape of the boat hull and to solidly support the boat in a generally horizontal position. The lift was moved between a lowered position in which the lifting arms and the cradles carried thereby were below the surface of the water so that a boat to be lifted may be floated in place above the raised position in which the boat hull supported on the cradle is lifted clear of the water. The lift arms were moved between their raised and lowered positions by means of a winch and cable arrangement driven by two independent electric motor and gear sets driving a respective winch. However, because the effective diameter of the cable wrapped around the winches, and because the speeds of the two motors may vary slightly, it was not possible to ensure that both sides of the lift would be raised or lowered uniformly such that the lift with the boat supported thereon would remain substantial horizontal as it was raised and lowered. Further, the provision of gear speed reducers coupled to each of the motors for driving the winches in a salt water environment resulted in the requirement of frequent maintenance and repair of these prior winch-operated boat docks and lifts.